This invention pertains to a piston and connecting rod assembly, and more particularly to an improved piston and connecting rod assembly for compressors and internal combustion engines, such as small two and four cycle engines, for example. A one-piece yoke thrust bearing is disposed between the piston and connecting rod to provide bearing surfaces therebetween.
In many engines, the connecting rod is guided either by shoulders on the crankshaft or by wrist pin bosses in the piston. Copending application Ser. No. 437,363 filed Oct. 25, 1982 discloses a prior art crankshaft and connecting rod assembly wherein the connecting rod is not guided on the crankshaft, and suitable bearings within the piston must be provided.
Current pistons for guiding the connecting rod in the piston generally comprise a pair of wrist pin bosses, wherein the bosses have oppositely disposed and spaced-apart faces, which have a smooth hard finish, and a pair of bores disposed through the respective bosses. One end of a connecting rod having an opening therethrough is disposed between the boss faces, and a washer is positioned between each face and one side of the connecting rod to provide bearing surfaces therebetween. A wrist pin is then passed through the boss bores, the two washers, and the opening in the connecting rod.
In assembling the above type piston and connecting rod assembly, one of the major difficulties is passing the wrist pin through the bores, both washers, and the connecting rod opening without displacing one of the washers out of axial alignment or dropping one of the washers out of the piston. This assembly is also quite time consuming since it requires the assembler to first align one of the washers with a bore, pass the wrist pin through the bore and through the washer, then insert the connecting rod and pass the pin through the connecting rod opening, and then align the second washer between the connecting rod and the other bore so that the wrist pin may then be passed therethrough. Clearly, multiple repetitions of this manual method of assembling will increase the likelihood of washers becoming displaced, dropped out of the piston, or possibly result in the assembling of the piston and connecting rod with only one washer.
Although the use of a stacking pin eliminates the necessity of individually aligning the washers and connecting rod with the wrist pin, it nevertheless is time consuming in that the operator must handle three items, i.e., two washers and the connecting rod, in assembling the piston and connecting rod together.
Further, most currently used washers are made of hardened and ground steel, and are therefore individually quite costly, and increase the overall cost of the engine.